The authors analyzed RI scan and ultrasonographic findings of 70 patients of thyroid diseases which were proven pathologically at Seoul Red Cross Hospital. The results were as follows : 1. The incidence was predominent in female. 2. Malignancy showed solitary cold nodule and solid or mixed echopattern with decreased echogenicity. 3. Hot nodules and cystic or hyperechoic nodules were represented all benign. 4. The appearance of margins my not be helpful in differentiating benign lesions from malignant lesions.